Circuit Description
When the brake pedal is depressed, the contacts on the brake light switch close to illuminate the brake lights. Battery voltage is also applied to terminal 14 of the electronic brake control module (EBCM), which signals the antilock brake system (ABS) controller that the brakes are applied and ABS may be needed. Without this, signals from a wheel speed sensor that may indicate a need for ABS intervention are questionable. When the brake pedal is not depressed, the EBCM terminal 14 is grounded through the brake lights.
This procedure will check whether there is no output or constant output from the brake light switch and will determine the cause as a faulty switch or a problem in the circuitry.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0161 Stop Lamp Switch Circuit Open
Conditions for Running the DTC
| • | Vehicle speed is greater than 6 km/h (4 mph) with the brake pedal not applied. |
| OR |
| • | Vehicle speed is greater than 15 km/h (9 mph) and the brake pedal is actuated. |
Conditions for Setting the DTC
| • | The ground connection or the positive connection at the EBCM has failed. |
| • | There is an open, short to ground, or short to positive in the vehicle wiring. |
| • | The brake light switch has failed. |
Action Taken When the DTC Sets
The system records a DTC C0161.
Conditions for Clearing the DTC
The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.
Diagnostic Aids
Inspect wiring and connectors carefully and thoroughly. Failure to do so could result in misdiagnosis, causing part replacement with reappearance of the malfunction.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This is the 1st step in identifying an open, a short to ground, a short to voltage, or a faulty brake light switch.
-
This step begins the process of finding an open, a poor connection, or a faulty EBCM.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 | Step on the brake pedal. Do the brake lights turn ON? | -- | Go to Step 4 | Go to Step 3 |
3 | Release the brake pedal. Do the brake lights stay ON? | -- | Go to Step 9 | Go to Step 12 |
Inspect fuse Ef4 in the engine compartment fuse block. Is fuse Ef4 open? | -- | Go to Step 5 | Go to Step 7 | |
5 |
Is the new fuse open? | -- | Go to Step 6 | Go to Step 8 |
6 |
Did you complete the action? | -- | Go to Step 17 | -- |
7 | Repair the open in the brake light switch circuit from terminal 26 of connector C102 at the engine fuse block to the brake light switch and to the terminal 30 of connector C 103. Did you complete the repair? | -- | Go to Step 17 | -- |
8 | Inspect for functioning of the brake lights and the antilock brake system (ABS) system. Did you complete the action? | -- | Go to Step 17 | -- |
9 | Inspect the brake lamp switch adjustment. Did the switch adjustment correct the condition? | -- | Go to Step 17 | Go to Step 10 |
10 | Replace the brake lamp switch. Refer to Stop Lamp Switch Replacement . Did you complete the repair? | -- | Go to Step 17 | -- |
11 | Repair the short in the circuit between the brake light switch, connector C 201, the brake lights, the center high-mounted stop lamp, and terminal 16 of the electronic brake control module (EBCM) connector. Did you complete the repair? | -- | System OK | -- |
Does the voltage measure within the specified range? | 11-14 V | Go to Step 13 | Go to Step 12 | |
13 |
Did you complete the repair? | -- | Go to Step 16 | -- |
14 | Inspect the interface between the EBCM connector and the EBCM. Is there damage at the interface? | -- | Go to Step 15 | Go to Step 16 |
15 | Repair the connector or replace the wiring harness or the brake pressure modulator valve (BPMV) as required. Did you complete the repair? | -- | Go to Step 17 | -- |
16 | Replace the BPMV. Refer to Brake Pressure Modulator Valve Assembly Replacement . Did you complete the replacement? | -- | Go to Step 17 | -- |
17 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
